1.Development of Ultrasonic probe with focusing sensorAn ultrasonic probe with focusing sensor was newly developed to improve the evaluation performance by back-scattering method for fatigue-creep damage. The probes were applied to damaged materials but no distinct improvement was observed compared with the normal probe type. It was shown that the improvement of measuring system is more important for the measuring accuracy.2.Development of Ultrasonic measuring systemAn Ultrasonic measuring system, which is composed of Work Station, pulser-receiver and digital oscilloscope, was developed. Aided by high performance of Work Station, the on-line real-time processing of the pressure load of the probe was developed using the DC solenoid. This greatly improves the measuring accuracy of ultrasonic properties.3.Development of quasi-damaged specimen for creep-fatigue damageQuasi-damaged materials with life ratio from 25% to 100% were made experimentally. The material is Cr-Mo-V Steel, which is often used as Rotor material in the electric power plant.4.Development of evaluation method for damaged matcrials using inverse problem techniqueTwo evaluation methods for damaged materials were newly developed in addition to the normal ultrasonic attenuation method. One is a noise energy method which evaluates the damage by integrating the power spectrum of back-scattering wave and normalizing it. The other is a weighted noise energy method which also utilize integral of the spectrum but calculated under the weighted function.5.ResultIt was shown that the proposed weighted noise energy method has great advantage that the damage evaluation is not affected by the integral range of frequency. Moreover, the proposed noise energy method was found to have superior properties for the evaluation of damaged material compared with the normal ultrasonic attenuation method.